There is a continuing need in various scientific and industrial fields for fluorescent dyes which exhibit high quantum efficiencies providing improved sensitivity. For example, the staining of bilogical tissues and cells with fluorescent dyes in order to differentiate one type from another or to render them more observable is well known in the art. Red fluorescent dyes are especially desirable because they are highly visible.
Further, chemical analysis of liquids, such as water, milk and biological fluids is often desirable or necessary for health maintenance and diagnostic care. Various compositions and elements to facilitate such analyses are known. Such materials generally include a reagent composition for determining a substance under analysis, identified as an "analyte" herein. The analyte can be a living organism, such as a microorganism or yeast cell, or a nonliving chemical substance. The reagent composition, upon interaction with the analyte, provides a detectable change (e.g. dye formation or dye release).
Recently, much work has been directed to developing compositions and elements which are useful for rapid and highly quantitative diagnostic or clinical analysis of biological fluids such as whole blood, sera, plasma, urine and the like. For example, for the rapid and effective diagnosis and treatment of infectious diseases, it is desirable to be able to detect the bacteria causing the disease as rapidly as possible. Infections of the urinary tract are among the most common bacterial diseases, second in frequency only to infections of the respiratory tract.
In U.S. Ser. No. 824,766, filed on even date herewith by Belly et al and entitled Reducible Compounds and Analytical Compositions, Elements and Methods Utilizing Same, novel reducible compounds are described and claimed which are useful in the detection of bacteria and other analytes. The assays of Belly et al provide colorimetric and fluorometric dyes in the presence of the analyte.
It is generally known that fluorescent dyes are more sensitive than colorimetric dyes in many biological assays. A variety of fluorescent dyes have been used in such assays, including the Belly et al assays. Such dyes include, for example, coumarins, fluorescein derivatives, phenalenones, benzphenalenones, spiroacridines and umbelliferone derivatives. Some of these dyes emit radiation in the red region of the spectrum. While the Belly et al assays represent a significant advance in the art, it would be useful to have additional dyes which have high quantum efficiencies and excellent sensitivity.